SoroushVahidi/scidocs huggingface dataset:
Generalized schema-mappings: from termination to tractability
(2009)

Data-Exchange is the problem of creating new databases according to a high-level specification called a schema-mapping while preserving the information encoded in a source database. This paper introduces a notion of generalized schema-mapping that enriches the standard schema-mappings (as defined by Fagin et al) with more expressive power. It then proposes a more general and arguably more intuitive notion of semantics that rely on three criteria: Soundness, Completeness and Laconicity (non-redundancy and minimal size). These semantics are shown to coincide precisely with the notion of cores of universal solutions in the framework of Fagin, Kolaitis and Popa. It is also well-defined and of interest for larger classes of schema-mappings and more expressive source databases (with null-values and equality constraints). After an investigation of the key properties of generalized schema-mappings and their semantics, a criterion called Termination of the Oblivious Chase (TOC) is identified that ensures polynomial data-complexity. This criterion strictly generalizes the previously known criterion of Weak-Acyclicity. To prove the tractability of TOC schema-mappings, a new polynomial time algorithm is provided that, unlike the algorithm of Gottlob and Nash from which it is inspired, does not rely on the syntactic property of Weak-Acyclicity. As the problem of deciding whether a Schema-mapping satisfies the TOC criterion is only recursively enumerable, a more restrictive criterion called Super-weak Acylicity (SwA) is identified that can be decided in Polynomial-time while generalizing substantially the notion of Weak-Acyclicity.
Ontology-Based Data Access: Ontop of Databases
(2013)

We present the architecture and technologies underpinning the OBDA system Ontop and taking full advantage of storing data in relational databases. We discuss the theoretical foundations of Ontop: the tree-witness query rewriting, T -mappings and optimisations based on database integrity constraints and SQL features. We analyse the performance of Ontop in a series of experiments and demonstrate that, for standard ontologies, queries and data stored in relational databases, Ontop is fast, efficient and produces SQL rewritings of high quality.
Linking Data to Ontologies
(2008)

Many organizations nowadays face the problem of accessing existing data sources by means of flexible mechanisms that are both powerful and efficient. Ontologies are widely considered as a suitable formal tool for sophisticated data access. The ontology expresses the domain of interest of the information system at a high level of abstraction, and the relationship between data at the sources and instances of concepts and roles in the ontology is expressed by means of mappings. In this paper we present a solution to the problem of designing effective systems for ontology-based data access. Our solution is based on three main ingredients. First, we present a new ontology language, based on Description Logics, that is particularly suited to reason with large amounts of instances. The second ingredient is a novel mapping language that is able to deal with the so-called impedance mismatch problem, i.e., the problem arising from the difference between the basic elements managed by the sources, namely data, and the elements managed by the ontology, namely objects. The third ingredient is the query answering method, that combines reasoning at the level of the ontology with specific mechanisms for both taking into account the mappings and efficiently accessing the data at the sources.
Data Integration: A Theoretical Perspective
(2002)

Data integration is the problem of combining data residing at different sources, and providing the user with a unified view of these data. The problem of designing data integration systems is important in current real world applications, and is characterized by a number of issues that are interesting from a theoretical point of view. This document presents on overview of the material to be presented in a tutorial on data integration. The tutorial is focused on some of the theoretical issues that are relevant for data integration. Special attention will be devoted to the following aspects: modeling a data integration application, processing queries in data integration, dealing with inconsistent data sources, and reasoning on queries.
Self-Adaptive Systems in Organic Computing: Strategies for Self-Improvement
(2018)

With the intensified use of intelligent things, the demands on the technological systems are increasing permanently. A possible approach to meet the continuously changing challenges is to shift the system integration from design to run-time by using adaptive systems. Diverse adaptivity properties – so-called self* properties – form the basis of these systems and one of the properties is self-improvement. It describes the ability of a system not only to adapt to a changing environment according to a predefined model, but also the capability to adapt the adaptation logic of the whole system. In this paper, a closer look is taken at the structure of self-adaptive systems. Additionally, the systems’ ability to improve themselves during run-time is described from the perspective of Organic Computing. Furthermore, four different strategies for self-improvement are presented, following the taxonomy of self-adaptation suggested by Christian Krupitzer et al.
Design and Evaluation of a High-Frequency LTCC Inductor Substrate for a Three-Dimensional Integrated DC/DC Converter
(2013)

High operating frequency and integration technique are two main approaches to achieve high power density for the switching mode power supply. The emerging gallium nitride (GaN)-based power device enables a multimegahertz high-efficiency point-of-load (POL) converter with high current capability. The low-temperature cofire ceramic (LTCC)-based integration technique successfully extends the three-dimensional (3-D) integrated POL module from the low current level to the high current level (>10 A). This paper presents the low-profile LTCC inductor substrate design and evaluation for a multimegahertz 3-D integrated POL converter with large output current. The detailed study about the impact of frequency on the LTCC inductor shows that the high frequency not only shrinks the volume of the inductor, but also simplifies the inductor structure. The comparison between the LTCC inductor and the discrete inductor demonstrates that the LTCC inductor dramatically boosts the converter light-load efficiency due to its nonlinear inductance. Because of the low-profile design, the power density of the single-phase POL module with LTCC inductor achieves 1.1 kW/in3 at 5 MHz. The performance of the LTCC inductor can be further improved by the inverse coupling, which results in more than 40% core thickness and core loss reduction. Therefore, the power density of a two-phase integrated POL module is pushed to 1.5 kW/in3, which is around ten times of the power density of state-of-the-art industry products with the same current level.
Which Predictability Measures Affect Content Word Durations
(2002)

The pronunciation of a word can vary widely, and many factors are known to affect this variation. This paper focuses on the role of predictability on word duration. Previous research has suggested that more frequent words are shorter, as are words which are more predictable from neighboring words. This research has tended to focus only on extremely high frequency function words; previous research on content words has not been able to examine natural speech and control for key confounding factors like accent and rate of speech. We examined 1401 content words from the Switchboard corpus and studied the role of word frequency, conditional and joint probabilities with neighboring words and a measure of word semantic association, Latent Semantic Analysis. Using multiple regression to control for confounding factors, we show that two predictability variables principally affect a word’s duration—word frequency, and the conditional probability of a word given the following word. Other predictability variables do not make an additional significant contribution. We discuss the implications for pronunciation modeling.
A GENETIC ALGORITHM FOR STRUCTURAL OPTIMIZATION OF STEEL TRUSS ROOFS
(2005)

A common structural design problem is the weight minimization of structures which is formulated selecting a set of design variables that represent the structural and architectural configuration of the system. The structures are usually subject to stress and displacement constraints and the design variables can be continuous or discrete. In practice, it is often desirable to choose design variables (such as cross-sectional areas) from commercially available sizes. The use of a continuous optimization procedure – although usually more straightforward – will lead to non-available sizes and any attempt to substitute those values by the closest available commercial sizes can make the design unfeasible or unnecessarily heavier. In this paper a genetic algorithm is proposed to evolve the structural configuration for weight minimization of industrial buildings, with rectangular geometry projection, made up of uniform planar structures (steel truss roofs) along the longitudinal direction which are interconnected by purlins. The planar structures are trusses and their number, shape, and topology are allowed to change during the optimization process.
C-OPT: Coverage-Aware Trajectory Optimization Under Uncertainty
(2016)

We introduce a new problem of continuous, coverage-aware trajectory optimization under localization and sensing uncertainty. In this problem, the goal is to plan a path from a start state to a goal state that maximizes the coverage of a user-specified region while minimizing the control costs of the robot and the probability of collision with the environment. We present a principled method for quantifying the coverage sensing uncertainty of the robot. We use this sensing uncertainty along with the uncertainty in robot localization to develop C-OPT, a coverage-optimization algorithm which optimizes trajectories over belief-space to find locally optimal coverage paths. We highlight the applicability of our approach in multiple simulated scenarios inspired by surveillance, UAV crop analysis, and search-and-rescue tasks. We also present a case study on a physical, differential-drive robot. We also provide quantitative and qualitative analysis of the paths generated by our approach.
Compact Ultrawideband MIMO Antenna With Half-Slot Structure
(2017)

In this letter, a multiple-input–multiple-output (MIMO) antenna with very compact size of only <inline-formula> <tex-math notation="LaTeX">$\text{23}\times \text{18}\; \text{mm}^{2}$</tex-math></inline-formula> is proposed for ultrawideband (UWB) applications. The proposed MIMO antenna consists of two symmetrical half-slot antenna elements with coplanar waveguide-fed structures and a Y-shaped slot that is cut at the bottom center of the common ground plane. The slot efficiently prevents the current from directly flowing between two ports at low UWB frequency. For such a compact-size antenna, the ground plane works as a radiator as well as a reflector that reflects the radiation from radiators at high frequency. The measured impedance bandwidth for <inline-formula><tex-math notation="LaTeX"> $S_{11}, S_{22}$</tex-math></inline-formula> < −10 dB is from 3 to 12.4 GHz. The measured mutual coupling for <inline-formula><tex-math notation="LaTeX">$S_{12}, S_{21}$</tex-math></inline-formula> < −15 dB is from 3 to 4 GHz and for <inline-formula><tex-math notation="LaTeX">$S_{12}, S_{21}$ </tex-math></inline-formula> < −20 dB is from 4 to 12.4 GHz. The proposed antenna also contains relatively stable radiation patterns and gains. These performances indicate that the proposed antenna is one competitive candidate for UWB applications.
AUV SLAM using forward/downward looking cameras and artificial landmarks
(2017)

Autonomous underwater vehicles (AUVs) are usually equipped with one or more optical cameras to obtain visual data of underwater environments. The camera can also be used to estimate the AUV's pose information, along with various navigation sensors such as inertial measurement unit (IMU), Doppler velocity log (DVL), depth sensor, and so on. In this paper, we propose a vision-based simultaneous localization and mapping (SLAM) of AUVs, where underwater artificial landmarks are used to help visual sensing of forward and downward looking cameras. Three types of landmarks are introduced and their detection algorithms are organized in a framework of conventional extended Kalman filter (EKF) SLAM to estimate both robot and landmark states. The proposed method is validated by an experiment performed in a engineering basin. Since DVL suffers from noises in a real ocean environment, we generated synthetic noisy data based on the real sensor data. With this data we verify that the proposed SLAM approach can recover from the erroneous dead reckoning position.
A 1.8V CMOS chopper four-quadrant analog multiplier
(2017)

A 1.8V CMOS chopper four-quadrant analog multiplier, intending to serve as an autonomous IC block for low-frequency signal processing, is presented. Particular emphasis is laid upon achieving low output noise by means of chopper stabilization, while the multiplier's operation is based on the MOS Translinear Principle. The proposed design has been implemented and simulated in TSMC 0.18 µm CMOS process.
A broadband compact low-loss 4×4 Butler Matrix in CMOS with stacked transformer based quadrature couplers
(2016)

This paper presents an ultra-broadband ultracompact Butler Matrix design scheme. The design employs stacked transformer based couplers and lumped LC π-network phase shifters for substantial size reduction. As a proof-of-concept design, a 4×4 Butler Matrix is implemented in a standard 130nm bulk CMOS process at a center frequency of 2.0 GHz. Compared with reported fully integrated 2.0 GHz 4×4 Butler Matrix designs in CMOS, the proposed design achieves the lowest insertion loss of 1.10dB, the smallest amplitude mismatch of 0.3 dB, the largest fractional bandwidth of 34.6%, and the smallest chip core area of 0.635×1.122 mm2. Based on the measured S-parameters, the four concurrent electrical array patterns of the Butler Matrix achieve array peak-to-null ratio (PNR) of 29.5 dB at 2.0 GHz and better than 15.0 dB between 1.55 GHz and 2.50 GHz.
A high accuracy solver for RTE in underwater optical communication path loss prediction
(2018)

In this paper, we present a new improved numerical framework to evaluate the time-dependent radiative transfer equation (RTE) for underwater optical wireless communication (UOWC) systems. The RTE predicts the optical path-loss of light in an underwater channel, as a function of the inherent optical properties (IOPs) related to the water type, namely the absorption and scattering coefficients as well as the phase scattering function (PSF). We reach the simulation performance based on an improvement of the finite difference scheme proposed in [1] as well as an enhancement of the quadrature method aiming to calculate the integral term of the RTE [2]. Additionally, we evaluate the received power at the receiver plane in three dimensions by considering a given receiver aperture and a field of view (FOV). Finally, we evaluate the UOWC system's bit error rate performance metric as a function of the propagation distance, and time.
Interlocking obfuscation for anti-tamper hardware
(2013)

Tampering and Reverse Engineering of a chip to extract the hardware Intellectual Property (IP) core or to inject malicious alterations is a major concern. Digital systems susceptible to tampering are of immense concern to defense organizations. First, offshore chip manufacturing allows the design secrets of the IP cores to be transparent to the foundry and other entities along the production chain. Second, small malicious modifications to the design may not be detectable after fabrication without anti-tamper mechanisms. Some techniques have been developed in the past to improve the defense against such attacks but they tend to fall prey to the increasing power of the attacker. We present a new way to protect against tampering by a clever obfuscation of the design, which can be unlocked with a specific, dynamic path traversal. Hence, the functional mode of the controller is hidden with the help of obfuscated states, and the functional mode is made operational only on the formation of a specific interlocked Code-Word during state transition. No comparator is needed as the obfuscation is embedded within the transition function of the state machine itself. A side benefit is that any small alteration will be magnified via the obfuscated design. In other words, an alteration to the design will manifest itself as a large difference in the circuit's functionality. Experimental results on an Advanced Encryption Standard (AES) circuit from the open-source IP-cores suite suggest that the proposed method provides better active defense mechanisms against attacks with nominal (7.8%) area overhead.
A printed antenna array fed by balanced Schiffman shifter used for UWB location system
(2015)

A double-sided printed bow-tie antenna array fed by balanced Schiffman phase shifter, which used as a reader antenna in ultra-wideband (UWB) location system, is proposed in this paper. The presented antenna has a impedance bandwidth of 3.4-4.4 GHz and a high gain of more than 5dB within the whole bandwidth. Good omnidirectional radiation pattern is obtained in the plane of θ = 15°. Good simulation results are achieved by HFSS.
Building event-centric knowledge graphs from news
(2016)

Knowledge graphs have gained increasing popularity in the past couple of years, thanks to their adoption in everyday search engines. Typically, they consist of fairly static and encyclopedic facts about persons and organizations – e.g. a celebrity’s birth date, occupation and family members – obtained from large repositories such as Freebase or Wikipedia. In this paper, we present a method and tools to automatically build knowledge graphs from news articles. As news articles describe changes in the world through the events they report, we present an approach to create Event-Centric Knowledge Graphs (ECKGs) using state-of-the-art natural language processing and semantic web techniques. Such ECKGs capture long-term developments and histories on hundreds of thousands of entities and are complementary to the static encyclopedic information in traditional knowledge graphs. We describe our event-centric representation schema, the challenges in extracting event information from news, our open source pipeline, and the knowledge graphs we have extracted from four different news corpora: general news (Wikinews), the FIFA world cup, the Global Automotive Industry, and Airbus A380 airplanes. Furthermore, we present an assessment on the accuracy of the pipeline in extracting the triples of the knowledge graphs. Moreover, through an event-centered browser and visualization tool we show how approaching information from news in an event-centric manner can increase the user’s understanding of the domain, facilitates the reconstruction of news story lines, and enable to perform exploratory investigation of news hidden facts. © 2016 Elsevier B.V. All rights reserved.
Information Bottleneck Inspired Method For Chat Text Segmentation
(2017)

We present a novel technique for segmenting chat conversations using the information bottleneck method (Tishby et al., 2000), augmented with sequential continuity constraints. Furthermore, we utilize critical non-textual clues such as time between two consecutive posts and people mentions within the posts. To ascertain the effectiveness of the proposed method, we have collected data from public Slack conversations and Fresco, a proprietary platform deployed inside our organization. Experiments demonstrate that the proposed method yields an absolute (relative) improvement of as high as 3.23% (11.25%). To facilitate future research, we are releasing manual annotations for segmentation on public Slack conversations.
Neurofeedback treatment for attention-deficit/hyperactivity disorder in children: a comparison with methylphenidate.
(2003)

Clinical trials have suggested that neurofeedback may be efficient in treating attention-deficit/hyperactivity disorder (ADHD). We compared the effects of a 3-month electroencephalographic feedback program providing reinforcement contingent on the production of cortical sensorimotor rhythm (12-15 Hz) and betal activity (15-18 Hz) with stimulant medication. Participants were N = 34 children aged 8-12 years, 22 of which were assigned to the neurofeedback group and 12 to the methylphenidate group according to their parents' preference. Both neurofeedback and methylphenidate were associated with improvements on all subscales of the Test of Variables of Attention, and on the speed and accuracy measures of the d2 Attention Endurance Test. Furthermore, behaviors related to the disorder were rated as significantly reduced in both groups by both teachers and parents on the IOWA-Conners Behavior Rating Scale. These findings suggest that neurofeedback was efficient in improving some of the behavioral concomitants of ADHD in children whose parents favored a nonpharmacological treatment.
An ultra-wideband absorber based on multiple resonators in 3-D frequency-selective structure
(2017)

An ultra-wideband absorber based on employing multiple resonators in the unit cell of a 3-D frequency-selective structure is proposed. The original design consists of two-dimensional periodic array of three-dimensional unit cells and lumped components to provide matching with free space and absorb the incident electromagnetic wave. By introducing one more resonator in the unit cell, an ultra-wideband absorber can be constructed. It has a fractional bandwidth of 155.7 % for −10 dB of reflection coefficient under the normal incidence with an absorber thickness of 0.12 λ0 at the lowest absorption frequency. This absorber works for TE polarization at which two quasi-TEM modes are excited in the air and substrate regions. The proposed absorber shows a stable performance under oblique angles of incidence.
Electrical and thermal processes of HEV induction machines taking into account stator winding form
(2017)

Internal combustion engine start processes in Hybrid Electric Vehicles (HEVs) are accompanied by large currents in the windings of electrical machines. It can lead to insulation overheating and fault operation mode. Induction squirrel-cage machine is one of the best AC machines for HEVs. The high efficiency of HEV induction machine with compact stator winding form is proposed. Its stator electrical and thermal processes are considered. Irregular cross-section of stator winding leads to irregular current density in particular winding parts. To decrease temperature gradients within induction machine and improve heat transfer, air gap between overhang parts and stator should be increased. Numerical and computer models for researching are based on finite element method.
TRESNEI, a Matlab trust-region solver for systems of nonlinear equalities and inequalities
(2012)

The Matlab implementation of a trust-region Gauss-Newton method for boundconstrained nonlinear least-squares problems is presented. The solver, called TRESNEI, is adequate for zero and small-residual problems and handles the solution of nonlinear systems of equalities and inequalities. The structure and the usage of the solver are described and an extensive numerical comparison with functions from the Matlab Optimization Toolbox is carried out.